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Engine sputters when hot

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  • Engine sputters when hot

    I've got a 79 CJ7 with a Pontiac 305 conversion out of a 1991 Firebird. The engine has over a hundred thousand miles on it and runs great, (plenty of power, no noises, etc...). Every so often, the previous owner and myself have experienced a sputtering, (like its starving for fuel) while driving on the trail, (engine temp at a normal 205 ish).
    I've tried to put a load on it (high RPM's) to no avail. The only thing that stops it is letting it cool down for a bit. It's very sporadic and has only happened twice in two years for me, (about 600 miles of driving). It has an aftermarket elec fuel pump, the tank is new as is the filter.
    Anyone have any ideas? Someone mentioned "vapor lock" however with it being so sporadic, I can't substantiate it.
    "It puts the Jeep on the rock"

  • #2
    is a tbi or port injection? I have had a somewhat simular vapor lock problem on tbi injections the pump made enough pressure to keep it running but not enough to open the regulator so it would not send fuel back to the tank. so when it got hot and you would let of the gas it would crap out. get it hot and checl the fuel pressure, is a good starting point if thats up to spec start looking at sparkplug wires sometimes the spark plug boots start arching through when hot and it starts dropping a cylinder

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    • #3
      Originally posted by aw12345 View Post
      is a tbi or port injection? I have had a somewhat simular vapor lock problem on tbi injections the pump made enough pressure to keep it running but not enough to open the regulator so it would not send fuel back to the tank. so when it got hot and you would let of the gas it would crap out. get it hot and checl the fuel pressure, is a good starting point if thats up to spec start looking at sparkplug wires sometimes the spark plug boots start arching through when hot and it starts dropping a cylinder
      Its TBI......Not sure how I check fuel pressure. In addition, I think I'll go ahead and replace the wires and plugs for good measure.
      "It puts the Jeep on the rock"

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      • #4
        You would T the gauge into the thicker fuel line of the 2

        fuel pressure should be somewhere between 10 to 13 psi if memory serves me correctly

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        • #5
          Originally posted by aw12345 View Post
          You would T the gauge into the thicker fuel line of the 2

          fuel pressure should be somewhere between 10 to 13 psi if memory serves me correctly
          You wouldn't happen to have one, would you?
          "It puts the Jeep on the rock"

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          • #6
            A pressure gauge? I am sure I can come up with one and some fittings to T it in

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            • #7
              Originally posted by aw12345 View Post
              A pressure gauge? I am sure I can come up with one and some fittings to T it in

              Yes, the pressure gauge. You mentioned something about rolling to Rat patrols shop re: cutting my corner guards and picking up aluminum (different thread under "V8 Engines"). Once I get with Kurt on the date(s), I'll sned them to u. If u can roll, let me know, and maybe we can gaudge it then. Thanks.
              "It puts the Jeep on the rock"

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              • #8
                We will figure something out. Riverside is not terribly far from Ontario as it is

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                • #9
                  Originally posted by aw12345 View Post
                  We will figure something out. Riverside is not terribly far from Ontario as it is
                  Copy that.......Thanks
                  "It puts the Jeep on the rock"

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